Forward- and backward-masked intensity discrimination measured using forced-choice and adjustment procedures

Area of Science:

• Auditory perception
• Psychoacoustics
• Sensory neuroscience

Background:

• Previous studies reported a "midlevel" hump in intensity just-noticeable differences (jnds) for pure tones under masker conditions.
• This phenomenon was observed using forced-choice procedures with a 100 ms signal-masker interval.
• Cognitive factors were hypothesized to influence results in traditional forced-choice intensity discrimination tasks.

Purpose of the Study:

• To investigate the influence of measurement paradigms on intensity discrimination jnds.
• To determine if cognitive factors contribute to the "midlevel hump" phenomenon.
• To compare intensity jnds obtained via forced-choice and method of adjustment.

Main Methods:

• Intensity jnds were measured using a "multiple-look" forced-choice method for forward-masked tones.
• Intensity jnds were measured using the method of adjustment for both forward- and backward-masked tones.
• Results were compared to jnds measured without a masker.

Main Results:

• Both standard and "multiple-look" forced-choice methods yielded intensity jnd data exhibiting a midlevel hump.
• The method of adjustment, for both forward and backward masking, did not produce a midlevel hump.
• Acoustic masker presence influenced intensity jnds differently depending on the measurement technique.

Conclusions:

• The "midlevel hump" in intensity jnds may be an artifact of forced-choice procedures, potentially influenced by cognitive factors.
• The method of adjustment may measure a different aspect of intensity discrimination than forced-choice methods.
• Further research is needed to clarify the underlying mechanisms of intensity discrimination and the role of measurement techniques.